The present invention relates to an exposure apparatus used for manufacturing, e.g., a semiconductor element, an image sensing element, a liquid crystal display element, a thin film magnetic head, and other microdevices.
In a photolithography process for manufacturing a semiconductor element and the like, an exposure apparatus has been used which projects the pattern image of a mask (e.g., a reticle) onto a photosensitive substrate through a projection optical system and exposes it. In recent years, development of a micropatterned semiconductor integrated circuit has been progressing, and in the photolithography process, the wavelength of a photolithography light source is becoming short.
As the exposure light, when a vacuum ultraviolet ray, particularly, a light beam with a wavelength shorter than 250 nm, e.g., harmonics of a KrF excimer laser (with a wavelength of 248 nm), an ArF excimer laser (with a wavelength of 193 nm), an (F2 laser (with a wavelength of 157 nm), or a YAG laser, or when X-rays are used, the intensity of the exposure light undesirably decreases because, e.g. the exposure light is absorbed by oxygen.
In view of this, conventionally, in an exposure apparatus having a light source such as an F2 excimer laser, a hermetically sealed space that seals only the optical path portion is formed. The gas in the hermetically sealed space is substituted by a gas not containing oxygen, e.g., nitrogen, so a decrease in transmittance of the exposure light is prevented.
FIG. 15 is a view showing an exposure apparatus in which an inert gas is supplied to an optical path space between the final optical member of a projection optical system (lens barrel) and a photosensitive substrate (wafer) so as to form an inert gas atmosphere in the optical path space, and exposure is performed. In this exposure apparatus, a shielding member is formed around the optical path space in order to separate the optical path space above the exposure region and an atmosphere surrounding it, and the inert gas is supplied to this space from around the exposure region. Hence, the inert gas concentration of the atmosphere in the optical path space can be set high.
In the exposure apparatus shown in FIG. 15, a temperature control gas is supplied to around the exposure region in order to stabilize the temperature of the surrounding atmosphere. The pressure increases slightly at that end of the wafer stage to which the temperature control gas is blown directly. As the wafer stage moves, the pressure distribution around the optical path space changes. In this case, the pressure in the optical path space also changes in accordance with a pressure change accompanying the movement of the wafer stage, and the concentration of the inert gas in the optical path space changes undesirably in accordance with the change in pressure. Consequently, the inert gas concentration is not stable.
As shown in FIGS. 16 and 17, an atmosphere surrounding the optical path space may be entrained when the stage moves. When the surrounding atmosphere flows in the +X direction, as shown in FIG. 16, the stage moving in the +X direction entrains an atmosphere present below nozzle 1 (space A). To the contrary, the stage moving in the xe2x88x92X direction entrains an atmosphere present below nozzle 2 (space B). Due to the flow of the surrounding atmosphere, most of an inert gas leaked from the optical path space exists below nozzle 2 (space B). The inert gas concentration becomes different between spaces A and B, and is higher in space B. The concentration of the inert gas which enters the optical path space changes depending on the stage moving direction, thus changing the inert gas concentration in the optical path space.
The same problem occurs when the inert gas is supplied to around a mask (e.g., a reticle). With the reticle as well, the inert gas concentration in the optical path space surrounded by a shielding member also changes, and the inert gas concentration is not stable.
The present invention has been made in view of the above problem, and has as its object to provide an exposure apparatus in which an inert gas concentration in an optical path space including a space through which exposure light passes (exposure region), such as a space between a projection optical system and a substrate, a space between an illumination optical system for illuminating a mask (e.g., a reticle) and a mask stage for holding the mask, and a space between the mask stage and the projection optical system, can be stabilized at high precision, a control method for the same, and a device manufacturing method.
According to the present invention, the foregoing object is attained by providing an exposure apparatus comprising:
an illumination optical system which illuminates a pattern formed on a mask with light from a light source;
a movable mask stage for holding the mask;
a projection optical system which guides light from a pattern of the mask to a wafer;
a movable wafer stage for holding the wafer;
a shielding member which forms an optical path space including an optical path of exposure light and a space surrounding the optical path space at, of a space through which the exposure light passes, at least one portion between said illumination optical system and said mask stage, between said mask stage and said projection optical system, or between said projection optical system and said wafer stage;
first gas supply means for supplying an inert gas to the optical path space; and
reduction means for reducing a change in total light quantity of the exposure light reaching the wafer that is caused by movement of said mask stage and/or said wafer stage.
In a preferred embodiment, said reduction means includes means for adjusting a light quantity which reaches the pattern of the mask.
In a preferred embodiment, said reduction means includes means for adjusting a light quantity of the light source.
In a preferred embodiment, said reduction means includes means for inserting a filter into the optical path of the exposure light from the light source.
In a preferred embodiment, said reduction means includes means for adjusting a stop arranged in the optical path of the exposure light from the light source.
In a preferred embodiment, said reduction means includes means for adjusting a driving speed of said mask stage and/or said wafer stage.
In a preferred embodiment, said reduction means is controlled based on at least one of positional information of said mask stage and/or said wafer stage, information about a moving speed, and information about a moving direction.
In a preferred embodiment, said apparatus further comprises a pressure sensor which measures a pressure in the optical path space, and
said reduction means is controlled in accordance with an output from said sensor.
In a preferred embodiment, said apparatus further comprises a concentration sensor which measures an oxygen concentration and/or a wafer concentration in the optical path space.
said reduction means is controlled in accordance with an output from said sensor.
In a preferred embodiment, said apparatus further comprises a second gas supply means for supplying a gas to the surrounding space.
In a preferred embodiment, said gas supplied by said second gas supply means is an inert gas.
In a preferred embodiment, said apparatus further comprises:
said shielding member which shields from the surrounding space a first optical path space between said wafer stage and said projection optical system,
wherein said first gas supply means supplies said inert gas toward a predetermined direction.
In a preferred embodiment, said apparatus further comprises:
said shielding member which shields from the surrounding space a first optical path space between said wafer stage and said projection optical system,
said shielding member shielding from the surrounding space a second optical path space between said illumination optical system and said mask stage and/or between said mask stage and said projection optical system, and
a supply port which supplies the inert gas to the first optical path space by said first gas supply means, and a supply port which supplies the inert gas to the second optical path space by said first gas supply means are formed at substantially opposite positions with respect to an optical axis of said illumination optical system and/or said projection optical system.
In a preferred embodiment, said reduction means adjusts an amount of the insert gas supplied to the optical path space and/or an amount of the gas exhausted from the optical space.
In a preferred embodiment, said reduction means adjusts an amount of the gas supplied to the surrounding space and/or an amount of the gas exhausted from the surrounding space.
In a preferred embodiment, said reduction means adjusts a light quantity of the exposure light with respect to a change in transmittance of the exposure light caused by movement of said mask stage and/or said wafer stage.
In a preferred embodiment, said apparatus includes a scanning exposure apparatus, and
said reduction means changes a scanning speed with respect to a change in transmittance of the exposure light caused by movement of said mask stage and/or said wafer stage.
In a preferred embodiment, said reduction means reduces a change in inert gas concentration in the optical path space.
In a preferred embodiment, said reduction means reduces a change in pressure difference between the optical path space and the surrounding space.
In still another aspect of the present invention, the foregoing object is attained by providing a device manufacturing method comprising the steps of:
transferring, by using the exposure apparatus defined in claim 1, a pattern onto a substrate applied with a photosensitive material; and
developing the substrate.
In still another aspect of the present invention, the foregoing object is attained by providing an exposure apparatus for projecting and transferring a pattern formed on a mask onto a substrate by using exposure light, comprising:
a stage;
an optical system;
a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between said stage and said optical system, including a space through which exposure light passes; and
control means for controlling a flow velocity or pressure of an atmosphere around said gas flow forming mechanism.
In a preferred embodiment, the apparatus further comprises:
a supply unit arranged around said gas flow forming mechanism to supply a gas; and
an exhaust unit arranged around said gas flow forming mechanism to exhaust the gas containing the inert gas.
In a preferred embodiment, said control means controls operation of at least one of said supply unit and said exhaust unit on the basis of a pressure in the optical path space.
In a preferred embodiment, said control means sets a supply amount of said supply unit to a constant value, and controls an exhaust amount of said exhaust unit on the basis of the pressure in the optical path space.
In a preferred embodiment, said control means sets an exhaust amount of said exhaust unit to a constant value, and controls a supply amount of said supply unit on the basis of a pressure in the optical path space.
In a preferred embodiment, said control means controls operation of at least one of said supply unit and said exhaust unit on the basis of a position of said stage.
In a preferred embodiment, said control means sets a supply amount of said supply unit to a constant value, and controls an exhaust amount of said exhaust unit on the basis of the position of said stage.
In a preferred embodiment, said control means sets an exhaust amount of said exhaust unit to a constant value, and controls a supply amount of said supply unit on the basis of the position of said stage.
In a preferred embodiment, said control means includes concentration measuring means for measuring a predetermined gas concentration in the optical path space, and controls operation of at least one of said supply unit and said exhaust unit on the basis of a measurement result of said concentration measuring means.
In a preferred embodiment, said control means sets a supply amount of said supply unit to a constant value, and controls an exhaust amount of said exhaust unit on the basis of the measurement result of said concentration measuring means.
In a preferred embodiment, said control means sets an exhaust amount of said exhaust unit to a constant value, and controls a supply amount of said supply unit on the basis of the measurement result of said concentration measuring means.
In a preferred embodiment, said control means includes concentration measuring means for measuring a predetermined gas concentration around the optical path space, and controls operation of at least one of said supply unit and said exhaust unit on the basis of a measurement result of said concentration measuring means.
In a preferred embodiment, said control means sets a supply amount of said supply unit to a constant value, and controls an exhaust amount of said exhaust unit on the basis of the measurement result of said concentration measuring means.
In a preferred embodiment, said control means sets an exhaust amount of said exhaust unit to a constant value, and controls a supply amount of said supply unit on the basis of the predetermined gas concentration around the optical path space.
In a preferred embodiment, said control means includes pressure measuring means for measuring a pressure around the optical path space, and controls operation of at least one of said supply unit and said exhaust unit on the basis of a measurement result of said pressure measuring means.
In a preferred embodiment, said control means sets a supply amount of said supply unit to a constant value, and controls an exhaust amount of said exhaust unit on the basis of the measurement result of said pressure measuring means.
In a preferred embodiment, said control means sets an exhaust amount of said exhaust unit to a constant value, and controls a supply amount of said supply unit on the basis of the measurement result of said pressure measuring means.
In a preferred embodiment, the predetermined gas is either one or a combination of the inert gas and a gas component, other than the inert gas, in an atmosphere.
In a preferred embodiment, said control means includes:
a first flow controller which controls a supply amount of said supply unit, and
a second flow controller which controls an exhaust amount of said exhaust unit.
In a preferred embodiment, said apparatus further comprises a chamber which hermetically seals an exposure apparatus main body including at least said stage, said optical system, and said gas flow forming mechanism, and
said supply unit and said exhaust unit are formed in part of said chamber.
In a preferred embodiment, said supply unit includes a plurality of supply units respectively connected to flow controllers and serves to supply the gas in a vertical direction, and
said control means controls operations of the plurality of supply units.
In a preferred embodiment, said control means controls operation of each of the plurality of supply units in accordance with a position of said stage.
In a preferred embodiment, said control means controls operation of each of the plurality of supply units in accordance with a predetermined gas concentration in the optical path space.
In a preferred embodiment, said control means controls operation of each of the plurality of supply units in accordance with a pressure in the optical path space.
In a preferred embodiment, the inert gas is nitrogen gas or helium gas.
In a preferred embodiment, said gas flow forming mechanism is arranged to form a flow of the inert gas in an optical path space between a projection optical system and a substrate.
In a preferred embodiment, said gas flow forming mechanism is arranged to form a flow of the inert gas in an optical path space between an illumination system for illuminating a mask and a mask stage for holding the mask.
In a preferred embodiment, said gas flow forming mechanism is arranged to form a flow of the inert gas in an optical path space between a mask stage for holding a mask and a projection optical system.
In a preferred embodiment, said gas flow forming mechanism includes:
a first gas flow forming mechanism arranged to form a flow of the inert gas in a first optical path space between a projection optical system and a substrate,
a second gas flow forming mechanism arranged to form a flow of the inert gas in a second optical path space between an illumination system for illuminating a mask and a mask stage for holding the mask, and
a third gas flow forming mechanism arranged to form a flow of the inert gas in a third optical path space between the mask stage and the projection optical system.
In still another aspect of the present invention, the foregoing object is attained by providing a control method for an exposure apparatus including a stage, an optical system, and a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between said stage and said optical system, including a space through which exposure light passes, to project and transfer a pattern formed on a mask onto a substrate by using exposure light, comprising the steps of:
measuring a pressure in the optical path space; and
controlling a flow velocity or pressure of an atmosphere around the gas flow forming mechanism on the basis of the pressure measured in the measuring step.
In still another aspect of the present invention, the foregoing object is attained by providing a device manufacturing method comprising the steps of:
transferring, by using an exposure apparatus, a pattern onto a substrate applied with a photosensitive material; and
developing the substrate,
the exposure apparatus including
a stage,
an optical system,
a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between the stage and the optical system, including a space through which exposure light passes, and
control means for controlling a flow velocity or pressure of an atmosphere around the gas flow forming mechanism.
In still another aspect of the present invention, the foregoing object is attained by providing an exposure apparatus for projecting and transferring a pattern formed on a mask onto a substrate by using exposure light, the apparatus comprising:
a stage;
an optical system;
a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between said stage and said optical system, including a space through which exposure light passes;
a first flow controller which controls a supply amount of the inert gas to be supplied to said gas flow forming mechanism;
a second flow controller which controls an exhaust amount of a gas containing the inert gas to be exhausted from said gas flow forming mechanism; and
control means for controlling operation of at least one of said first and second flow controllers.
In a preferred embodiment, said control means controls operation of at least one of said first and second flow controllers on the basis of a pressure in the optical path space.
In a preferred embodiment, said control means sets a supply amount of said first flow controller to a constant value, and controls an exhaust amount of said second flow controller on the basis of the pressure in the optical path space.
In a preferred embodiment, said control means sets an exhaust amount of said second flow controller to a constant value, and controls a supply amount of said first flow controller on the basis of the pressure in the optical path space.
In a preferred embodiment, wherein said control means controls operation of at least one of said first and second flow controllers on the basis of a position of said stage.
In a preferred embodiment, said control means sets a supply amount of said first flow controller to a constant value, and controls an exhaust amount of said second flow controller on the basis of the position of said stage.
In a preferred embodiment, said control means sets an exhaust amount of said second flow controller to a constant value, and controls a supply amount of said first flow controller on the basis of the position of said stage.
In a preferred embodiment, said control means controls operation of at least one of said first and second flow controllers on the basis of a predetermined gas concentration in the optical path space.
In a preferred embodiment, said control means sets a supply amount of said first flow controller to a constant value, and controls an exhaust amount of said second flow controller on the basis of the predetermined gas concentration in the optical path space.
In a preferred embodiment, said control means sets an exhaust amount of said second flow controller to a constant value, and controls a supply amount of said first flow controller on the basis of the predetermined gas concentration in the optical path space.
In a preferred embodiment, the predetermined gas is either one or a combination of the inert gas and a gas component, other than the inert gas, in an atmosphere.
In a preferred embodiment, said apparatus further comprises pressure measuring means for measuring a pressure around the optical path space, and
said control means controls operation of at least one of said first and second flow controllers on the basis of a measurement result of said pressure measuring means.
In a preferred embodiment, said control means sets a supply amount of said first flow controller to a constant value, and controls an exhaust amount of said second flow controller on the basis of the measurement result of said pressure measuring means.
In a preferred embodiment, said control means sets an exhaust amount of said second flow controller to a constant value, and controls a supply amount of said first flow controller on the basis of the measurement result of said pressure measuring means.
In a preferred embodiment, said apparatus further comprises concentration measuring means for measuring a concentration of a predetermined gas around the optical path space, and
said control means controls operation of at least one of said first and second flow controllers on the basis of a measurement result of said concentration measuring means.
In a preferred embodiment, said control means sets a supply amount of said first flow controller to a constant value, and controls an exhaust amount of said second flow controller on the basis of the measurement result of said concentration measuring means.
In a preferred embodiment, said control means sets an exhaust amount of said second flow controller to a constant value, and controls a supply amount of said first flow controller on the basis of the measurement result of said concentration measuring means.
In a preferred embodiment, the predetermined gas is either one or a combination of the inert gas and a gas component, other than the inert gas, in an atmosphere.
In still another aspect of the present invention, the foregoing object is attained by providing a control method for an exposure apparatus including a stage, an optical system, and a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between said stage and said optical system, including a space through which exposure light passes, to project and transfer a pattern formed on a mask onto a substrate by using exposure light, characterized by comprising the steps of:
measuring a pressure in the optical path space; and
controlling operation of at least one of first and second flow controllers on the basis of the pressure measured in the measuring step, the first flow controller serving to control a supply amount of the inert gas to said gas flow forming mechanism, and the second flow controller serving to control an exhaust amount of a gas containing the inert gas from said gas flow forming mechanism.
In still another aspect of the present invention, the foregoing object is attained by providing device manufacturing method comprising the steps of:
transferring, by using an exposure apparatus, a pattern onto a substrate applied with a photosensitive material; and
developing the substrate,
the exposure apparatus including
a stage,
an optical system,
a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between the stage and the optical system, including a space through which exposure light passes,
a first flow controller which controls a supply amount of the inert gas to be supplied to the gas flow forming mechanism,
a second flow controller which controls an exhaust amount of a gas containing the inert gas to be exhausted from the gas flow forming mechanism, and
controlling means for controlling operation of at least one of the first and second flow controllers.
According to the present invention, the foregoing object is attained by providing an exposure apparatus for projecting and transferring a pattern formed on a mask onto a substrate by using exposure light, comprising a stage, an optical system, a gas flow forming mechanism which forms a flow of an inert gas in an optical path space, between the stage and the optical system, including a space through which exposure light passes, and control means for controlling a flow velocity or pressure of an atmosphere around the gas flow forming mechanism.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.